java如何根据字符串的长度对其进行分组？

Question

public class sortingtext {

    public static void main(String[] args) throws IOException {
            String  readline="i have a sentence with words";
            String[] words=readline.split(" ");

            Arrays.sort(words, (a, b)->Integer.compare(b.length(), a.length()));

            for (int i=0;i<words.length;i++)
            {
                int len = words[i].length();

                int t=0;

                System.out.println(len +"-"+words[i]);
            }

        }

输入：

i have a sentence with words

我的代码拆分一个字符串，然后它应该打印每个单词及其长度

我得到的输出如下所示：

8- sentence

5- words

4- have

4-with

1-I

1-a

我想将相同长度的单词分组，得到：

8- sentence

5- words

4- have ,with

1- I ,a

但我不知道如何将它们分组

Answer 1

如果您是初学者或不熟悉stream API：

public static void main(String[] args) {
    String  readline= "i have a sentence with words";
    String[] words = readline.split(" ");
    Arrays.sort(words, (a, b)->Integer.compare(b.length(), a.length()));
    // declare a variable to hold the current string length
    int currLength = -1;
    for(int i = 0; i<words.length; i++){
        if(currLength == words[i].length()){
            // if currLength is equal to current word length just append a comma and this word
            System.out.print(", "+words[i]);
        }
        else{
            // if not update currLength, jump to a new line and print new length with the current word
            currLength = words[i].length();
            System.out.println();
            System.out.print(currLength+ " - "+words[i]);                
        }
    }
}

注：println（“…”）方法打印字符串“…”并将光标移动到新行。印刷品（“…”）方法只打印字符串“…”，但不会将光标移动到新行。因此，后续打印指令将在同一行上打印。println（）方法也可以在没有参数的情况下使用，以将光标定位到下一行

Answer 2

轻松使用流API：

final Map<Integer, List<String>> lengthToWords = new TreeMap<>(
    Arrays.stream(words)
        .collect(Collectors.groupingBy(String::length))
);

流按长度将单词分组到一个映射中（实现细节，但它将是一个HashMap），然后TreeMap根据关键字（单词长度）对该映射进行排序

或者，你可以这样写，效率更高，但在我看来可读性较差

final Map<Integer, List<String>> lengthToWords = Arrays.stream(words)
    .collect(Collectors.groupingBy(String::length, TreeMap::new, Collectors.toList()));